The present day commercial jet airliner utilizes a toilet waste system comprising a waste holding tank with a drain valve mounted in the bottom thereof, and flushing the toilet bowl with recirculating liquid.
Servicing of the toilet waste system is accomplished through a service panel which interconnects with the drain valve of the holding tank through a nominal four-inch diameter drain line. For servicing, a hose from a ground service tank truck is connected to the service panel, waste drain line connection; and the drain valve is opened by the service attendant pulling on a drain valve control handle. The toilet waste is drained by gravity from the waste holding tank through the drain line and over the airport ramp to be deposited into the ground service tank truck. After draining of the waste holding tank, for a cleansing action, water from the ground service tank truck is pumped into the tank through a flush connection on the service panel; and then, a small amount of pre-charge liquid is added and left in the waste holding tank for initiating toilet flushing action.
One of the problems with aircraft toilets has been caused by drain valve leakage; and the most frequent cause of this leakage has been due to particles of debris becoming trapped between the rubber drain valve and the valve seat, when it closes. This allows the liquid in the waste holding tank to drain into a four-inch diameter drain line which generally connects with the service panel. Now, if the hinged cap on the waste drain line connection at the service panel, seals the drain line tightly and does its job, then the only problem that a leaking rubber drain valve could cause, would be to permit the liquid from the waste holding tank to drain into the four-inch diameter drain line. However, some of the drain line installations of the larger type of commercial passenger airplanes, such as the Boeing 747, are of sufficient length so that the liquid level in the toilet bowl lowers to a level where the flushing action becomes inoperative. Another problem occurs when there is leakage from the hinged cap on the waste drain line connection at the service panel; because, the toilet waste liquid, which is very corrosive, leaks to the outside of the airplane and corrodes the exterior aluminum skin. Also, when this leakage occurs at high altitude, the liquid freezes onto the exterior surfaces of the airplane and keeps building up into large chunks of "Blue-Ice". The color is due to the blue dye additive in the waste holding tank which is utilized for masking the color of the waste matter. When this Blue-Ice becomes relatively large, or when the airplane descends to warmer air at a lower altitude, such as entering into a landing pattern, then this Blue-Ice becomes dislodged. There have been numerous incidents of damage to the airplane itself, from this Blue-Ice striking the leading edge of the wing and empenage surfaces, and being ingested into aft mounted engines. Also, there have been incidents of the falling Blue-Ice causing property damage.
Waste drain valve leakage, has been a problem to the airlines for a long time; and it is basically true, that if more servicing attention were given to the existing toilet systems and more preventive maintenance were performed, such as replacing the rubber drain valves, then the system would provide good service without leakage. However, the facts of the matter are, that this is not always done and some debris does become trapped under the rubber drain valve. The problem is, that when the drain valve does leak, it fills up the drain line with liquid waste all the way to the hinged cap at the service panel. Then, when the service attendant removes the cap for a servicing hook-up, he is inundated by the liquid waste and it also spills onto the airport ramp. This upsets everyone, including the airport authorities; and as a result of this, some of the airports in this country have legislated the use of a device known as a "Do-Nut". This Do-Nut comprises a rubber ring which is mounted onto an expandable metal hoop and requires a special fixture for inserting and removing it from the interior of the drain line in the vicinity of the hinged cap cover. The Do-Nut functions somewhat similar to that of an expandable rubber stopper on a thermos bottle. The Do-Nut, which is a loose item, occasionally gets lost or is thrown away; and the annual replacement cost to the airlines runs into the thousands of dollars. It also is prone to leakage; however, if it is used as directed, it does solve the problem of having the entire length of drain line emptying onto the airport ramp. Even if it does leak slightly, as long as it remains in position, only a small amount of liquid that is trapped between it and the removable cap cover, would spill out. However, this Do-Nut still doesn't solve the Blue-Ice problem at high altitude, where the pressure differential between the waste holding tank and the atmosphere forces liquid leakage into the drain line, past the Do-Nut and cap-cover seal, and onto the exterior skin surface of the airplane.
Therefore, the object of this invention is to solve these problems regardless of how good or how bad the toilet waste system is serviced.